Microemulsion synthesis and optical temperature sensor properties in HA/β-TCP composite phosphors

Area of Science:

• Materials Science
• Inorganic Chemistry
• Solid-State Physics

Background:

• Hydroxyapatite (HA) and beta-tricalcium phosphate (β-TCP) are biocompatible ceramic materials.
• Upconversion (UC) phosphors can convert lower energy photons to higher energy photons.
• Rare earth element doping is crucial for UC properties.

Purpose of the Study:

• To develop a novel microemulsion (ME) method for synthesizing rare earth-doped HA/β-TCP composite phosphors.
• To investigate the effect of polyvinyl alcohol (PVA) content on the phosphors' structure and luminescence.
• To evaluate the potential applications of these phosphors in thermal sensing and optoelectronics.

Main Methods:

• Microemulsion (ME) method for synthesizing composite phosphors.
• X-ray diffraction (XRD) and Raman spectroscopy for structural analysis.
• Upconversion (UC) luminescence spectroscopy under 975 nm excitation.
• Fluorescence intensity ratio (FIR) technique for temperature sensitivity measurement.

Main Results:

• The synthesized phosphors consisted of hexagonal HA and orthorhombic β-TCP phases.
• Intense green UC emission was observed, with intensity dependent on PVA content.
• High color purity (up to 94.77%) and significant temperature sensitivity (0.93% K⁻¹ at 293 K) were achieved.

Conclusions:

• The ME method is effective for producing HA/β-TCP composite phosphors with desirable UC properties.
• PVA content plays a critical role in tuning the luminescence characteristics.
• The developed phosphors show promise for advanced applications in thermal sensing and optoelectronic devices.